Counter circuit



May 3, 1960 J. B. ATWOOD COUNTER CIRCUIT Filed July 12, 1945 BY 177026! y COUNTER CIRCUIT John B. Atwood, Riverhead, N.Y., assign'or, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Appiieation July 12, 1945, Serial No. 604,574

4 Claims. (Cl. 328-193) This invention relates to counter circuits and has for its object to provide a circuit arrangement which will operate at very high speed to deliver a rectangular output wave having half the frequency of the input pulses. The invention falls within the class of counter circuits which utilizes two electron discharge tubes having cross-connec-,

vided for the purpose of accelerating the triggering action and in order to render the circuit more reliable in operation.

My invention will now be described in more detail, reference being made to the accompanying drawing the sole figure of which represents illustratively a preferred circuit arrangement.

United States Patent O Referring to the drawing, I show a circuit which is symmetrical in all respects. The parts which are given odd numbers are to be found on the left side of the diagram, whereas corresponding parts which are given even numbers are to be found on the right side of the diagram. On this account it will be suflicient to describe the left side only, but in explaining the operation both sides will,

of course, be referred to. Certain components of the circuit will be understood as common to the two sides and for this reason they are given reference characters which include letters andfigures.

In the diagram two input discharge tubes 1 and 2 are indicated as of the pentode type. Two main discharge tubes 3 and 4 of the trigger circuit proper are also of the pentode type.

Tube 1 contains a cathode 5, an anode 17 and three grids 9, 13 and 15. The tube 3 contains a cathode 7, an anode 19 and three grids 11, 13 and 15.

The cathodes are grounded. Anode-potential is supplied from any suitable direct current source, here indicated as having a positive terminal for supplying 250 volts above ground potential. This voltage is fed through a voltage dropping resistor 21 to the anode 19. By means of a further voltage dropping resistor 23 anode potential is also supplied to the anode 17 A relatively low'screen grid potential is supplied to the screen grids 13 in the two tubes 1 and 3. This screen grid potential may be obtained from a tap on a voltage'divider consisting of two resistive elements r2 and r3. For example, +50 volts may be chosen as the nominal screen grid potential. Resistor r3 is bypassed by a capacitor c1. I

An input circuit common to the two sides is shown connected to the control grids 9 and 10 in tubes 1 and 2. These grids are suitably biased with respect to their cathodes by means of a potentiometer 11 connected between ground and a negative potential source, here indicated as 2,935,689 Patented May 3, 1960 The movable tap on potentiometer p1 is ice 1.5 volts.

connected to the control grids 9 and 10 through a resistor 11. A capacitor c2 serves to bypass the grounded end portion of potentiometer p1. The suppressor grids 15 are connected to the grounded cathodes, as is conventional.

The control grid 11 in tube 3 is suitably biased with respect to the cathode 7 by means of a potentiometer p2 connected between ground and a source of biasing potential here indicated as -45 volts. The tap on the potentiometer p2 is connected to the grid 11 through a resistor 27. A capacitor 03 is connected between this tap and ground for bypassing high frequency currents.

A cross-connection 31 is shown for producing the control action between the output circuits of tubes 1 and 3 and the input circuit of tube 4. This control is obtained from tube 1 through a capacitor 29 and from tube 3 through a resistor 25. I

In the case of one illustrative embodiment of my invention which was built and tested under practical conditions it was found that by setting the tap on potentiometer p1 to an optimum position of adjustment tubes 1 and 2 could be caused to draw anode current of an amplitude which is substantially one-fifth that which would be drawn under conditions of zero bias. This adjustment will, therefore, be assumed.

The operation of the circuit will now be explained. Either side of the circuit may be conducting at any moment while the other side is biased to cut-off. Assume that tube 3 is in the conducting condition and tube 4 in the non-conducting condition. The anode voltage in tube 3 will be low due to the large voltage drop through resistor 21. Conversely, with tube 4 in a cut-ofi state, there will be a very low potential drop through resistor 22 and the anode voltage in tube 4 will be high. The anode voltage in tube 1 is determined by the voltage drop through resistors 21 and 23 in series. Since the voltage drop in resistor 21 is considerable, it will be still greater from the source to the anode 17. In tube 2, on the contrary, the voltage applied to anode 18 will be relatively high. This tube, therefore, is in a more favorable position to respond to a positive input pulse than tube 1.

Positive input pulses are applied simultaneously to the grids 9 and 10. They have no appreciable effect on tube 1 at this time since the anode potential therein, and, therefore, the susceptance, is very low. In tube 2 an amplifying action takes place and an electronic discharge starts with great suddenness. A surge impulse is, therefore,

applied across capacitor 30 which affects the control grid 7 11 in tube 3, and, due to its negative polarity, biasing this tube to cut-ofi. The consequent rise of potential on the anode 19 produces a current surge through resistors 25, 28 and the potentiometer p2 such that the grid 12 in tube 4- is positively biased. Tube 4 is now driven to the conductive state. The potential drop to the anode 20 produces a further controlling eifect upon the grid 11 in tube 3 so as to swing the bias on grid 11 far to the negative side. This stable state is, therefore, continued until the next positive pulse is received on the input circuit. The triggering action is aided by the fact that the reflex action from anode 18 in tube 2 upon the grid 11 in tube 3 is obtained through the capacitor 30 and this is faster than that which is obtainedthrough the resistor 26 as a result aeeaesa plied to its grid, the small negative pulse appearing on the anode 17 has a negligible effect on the operation of the circuit.-

After the circuit has triggered, the functions of tubes 1 and 3 on the one side and tubes 2 and 4 on the other side are "reversed and the circuit will then trigger back when the next positive pulse is applied to the input circuit, in a manner'similar to that which has just been described.

Output potentials of rectangular Wave form may be taken oli at any suitable point depending upon the polarity of these potentials as wanted in relation to the odd and even pulses applied to the input circuit. illustratively, however, the output is indicated as being obtained from the rise and fall of anode potential intube 4. Accordingly, output terminals 34- are illustratively shown where one of them is coupled to the anode 2t) acrossu capacitor 36, the other output terminal being grounded.

If it is desired that the output be fed into a push-pull circuit, then, of course, two output conductors may be provided, each being coupled to a respective one of the anodes 19 and 20.

It will, of course, be understood by those skilled in the art that modifications may be made without departing from the spirit and scope of the invention. The form in which the invention is illustrated and described is, therefore, to be considered as merely exemplary.

I claim:

1. A frequency divider of the aperiodic multivibrator type comprising two vacuum discharge devices each having a cathode, an anode and a plurality of grids, a direct current source connected from its negative terminal through an impedance to a point of reference potential at which said cathodes are maintained, said source being connected from its positive terminal through individual resistors to said anodes, a grid biasing circuit connected between the control grids of said devices and a voltage divider placed across a section of said source, resistive cross-connections between each said anode of one device and the control grid of the other said device, a pair of alternately controllable amplifier tubes each having its cathode directly connected to said point of reference potential and each having a resistive connection from its anode to the anode in a respective one of said vacuum discharge devices, and capacitive means for coupling each anode in said amplifier tubes to a respective one of said cross-connections, thereby to accelerate the triggering action between said devices.

2. A trigger circuit having two degrees of stability and of the type always requiring the application of a Wave of predetermined polarity to change its degree of stability, comprising two vacuum discharge devices each having an anode and a control grid, resistive cross-connections between each said anode of one device and the control grid of the other device for producing a triggering action, two electronic amplifier tubes having their input circuits connected in common to an outside source of pulses which are to be counted, each said tube having a grounded cathode and an individual resistive anode circuit of which only a portion is common to a respective one of the anode circuits of said devices, input circuit bias adjusting means for controlling the gain in said amplifier tubes, input circuit bias adjusting means in common to said vacuum discharge devices and independent of said first bias adjusting means for controlling the sensitivity of said vacuum discharge devices to triggering action, and .a capacitor coupled between the anode of each amplifier tube and the control grid of the device on the opposite side, whereby said triggering action is accelerated, each capacitor being in shunt to a series circuit composed of the non-common portion of its resistive anode circuit and a respective one of the resistive crosscouplings of the anode circuits of said devices.

3. A frequency divider of the double stability trigger circuit type comprising two vacuum discharge device electrode structures each having a cathode, an anode and a plurality of grids, a connection from each of said cathodes to ground, an adjustable source of bias for said grids including a potentiometer and a source of unidirectional potential connected across said potentiometer, individual resistors between the control grids of said structures and a point on said potentiometer, means for applying positive potentials to-said anodes through individual resistors, resistive cross-connections between each said anode of one structure and the control grid of the other structure, a pair of alternately controllable amplifier electrode sections each having its cathode directly connected to ground and each having a resistive connection from its anode to the anode in a respective one of said vacuum device electrode structures, and capacitive means coupling each anode in said amplifier'sections to a respective one of said crossconnections, thereby to accelerate the triggering action between .said discharge structures.

4. In combination, a trigger circuit having two degrees of electrical stability and of the type always requiring the application of a wave of predetermined polarity to change its degree of stability comprising first and second vacuum tube sections each having an anode, a control grid and a cathode, a resistor connecting the anode of each section to the control grid of the other section, a connection between said cathodes, a source of unidirectional current supplying voltages which are positive relative to said cathodes to said anodes through individual anode resistors, third and fourth alternately controllable multielectrode amplifier sections each having an anode, a resistor connecting the anode of said third section to the anode of said first section, and a resistor connecting the anode of said fourth section to the anode of said second section, whereby the anodes of said third and fourth sections obtain their anode polarizing potentials through the respective anode resistors of said first and second sections, a capacitor coupling the anode of said third section to the control grid of said second section, and a capacitor coupling the anode of said fourth section to the control grid of said first section, whereby the start of conduction in said third section causes the application of a relatively negative pulse to the grid of said second section and the simultaneous reduction of anode voltage in the first section, whereas the start of conduction in said fourth section causes the application of a relatively negative pulse to the grid of said first section and the simultaneous reduction of anode voltage in the second section.

References Qited in the file of this patent UNITED STATES PATENTS 1,976,384 Braman Oct. 9, 1934 2,365,5 12 Bartelink Dec. 19, 1944 2,366,357 Schlesinger Jan. 2, 1945 2,402,989 Dickinson July 2, 1946 OTHER REFERENCES Review of Scientific Instruments, November 1937, vol. 8, pages 414-416, A Vacuum Tube Circuit for Scaling Down Counting Rates, by Stevenson and Getting. 

